I HAVE a 1994 Ford F150 with a 5.0. All the cylinders are reading right at 150 on the compression check. Except one which is at around 130 and my number 4 cylinder is reading o nothing at all going on there. The truck still runs and isn't making any noises from the motor.

My question is what would cause this?
Is it more then likely the exhaust valve on that dead cylinder?

And is it possible to just change one valve?
Some one anyone please help me out

 

well you can use a air compressor and blow air into the cylinder to see if its coming out the exhaust pipe, intake or past the piston, which in that case it will come out the breather, also might be a blown head gasket.

 

Could be the rings. Squirt some oil in & retest those cylinders. How many rotations?

 

tried it and it still read zero let it rotate more then three or four times and the needle never moved was talking with a master tech. and he said that it very unlikely for the 5.0 to have a hole in the piston, he says its more then likely an intake valve or exhaust valve



what do you guys think?
just trying to find out how much trouble it is to change a valve

 

If it is a valve, might be easier getting a rebuilt head, they are not that expensive, but changing a valve requires removing cyl head, get a valve spring tool, remove spring, pull the valve out, you will want to carefully check the seat, if the seat is good you can get a valve and lap it in with lapping compound.